1. Field of the Invention
The present invention relates to a toroidal-type continuously variable transmission.
2. Description of the Related Art
Conventionally, as a toroidal-type continuously variable transmission, there is known an apparatus structured such that first and second continuously variable transmission mechanisms are disposed coaxially with each other: specifically, the first continuously variable transmission mechanism comprises a first input disk, a first output disk disposed so as to be opposed to the first input disk and a pair of power rollers respectively held between the first input and output disks; the second continuously variable transmission mechanism comprises a second input disk, a second output disk disposed so as to be opposed to the second input disk and a pair of power rollers respectively held between the second input and output disks; the first and second continuously variable transmission mechanisms are disposed such that the first and second input disks are disposed so as to be opposed to each other in the axial direction thereof; the first and second input disks are connected together so as to be rotated in synchronization with each other; and, the first and second output disks can be rotated integrally with each other.
By the way, for example, in JP-A-2000-104804 and U.S. Pat. No. 5,607,372, there is disclosed an apparatus in which the above-mentioned first and second output disks are structured as a unified type output disk including on the two sides thereof traction surfaces to be contacted with the above-mentioned pair of first power rollers and the above-mentioned pair of second power rollers.
However, the unified type output disk cannot be processed with high precision and, especially, the traction surfaces of the unified type output disk are difficult to work.
That is, when working the traction surfaces, there are necessary surfaces which can be used as machining datum. One of them is a datum surface which can be used to restrict the whirling of the unified type output disk in the rotation direction thereof; and as this datum surface, there is used a portion of the outside diameter portion of the unified type output disk. As the other datum surface, there is necessary a datum plane which is used to fix the unified output disk in the axial direction thereof. However, in the case of the unified type output disk disclosed in either of the above-cited JP-A-2000-104804 or U.S. Pat. No. 5,607,372, the plane of the near-to-inside diameter portion of the unified type output disk must be used as the machining datum surface; and, therefore, when working the traction surfaces, the whirling of the outside diameter portion of the unified type output disk increases, with the result that, when grinding or superfinishing the disk, the traction surfaces cannot be ground with high precision. Such poor surface precision of the traction surfaces not only can lower the power transmission efficiency of the unified type output disk but also can make the gear change operation thereof unstable.